The Teamsters union, threatened by government racketeering allegations, was welcomed back into the AFL-CIO yesterday, three decades after it was expelled for refusing to answer allegations of corruption.

The AFL-CIO president, Lane Kirkland, said the executive council of the 12.7 million-member labor federation voted "without opposition" yesterday to accept the Teamsters reaffiliation effective Nov. 1. He added that he "rather doubts" the Teamsters would have asked to rejoin without the threat of court action by the government.

The Teamsters president, Jackie Presser, has been invited to address the AFL-CIO convention on Thursday, Kirkland said. Officials of the union, the nation's largest with 1.6 million working members, had said earlier that Presser would accept the invitation.

Presser is scheduled to go on trial next March in Cleveland on federal charges of embezzlement.

In addition, law enforcement officials say the US Justice Department is preparing a civil racketeering lawsuit against the Teamsters, alleging a pattern of corruption during the past 13 years and seeking the replacement of all of its top officials with a court-appointed government trustee.

The federal crackdown on the Teamsters was perceived as a focal point of its application to rejoin the AFL-CIO. In addition to Kirkland's comments, The New York Times yesterday quoted unidentified law enforcement officials as saying the move could undercut the government's legal action.

"It will render it much more difficult and politically unpalatable to bring an action against the Teamsters when they are under the AFL-CIO's umbrella," the Times quoted one source as saying Friday.

Labor attorneys here acknowledged that the reaffiliation would pose political problems for an unprecedented attempt by the government to put an entire union under federal trusteeship, but said it raised no significant new legal issues for the contemplated suit.

Kirkland condemned what he called the government's "taking shortcuts around this tedious problem of dealing with individuals who are the object of these allegations and imprisoning the entire institution instead under the control of an appointee of the government."

But he denied that the AFL-CIO was offering the Teamsters a "shield or cover."

"I am committed to do everything I can to bind up the scattered leaves of this movement," Kirkland said. "This is a process of pursuing solidarity and bringing into one house all of labor's children."

Teamsters officials here would not speak on the record yesterday. But Duke Zeller, a spokesman for the Teamsters, said Thursday that an AFL-CIO statement in August condemning the proposed Justice Department suit was a factor in his union's decision to rejoin the federation.

"Certainly, it was a plus, and in the spirit of solidarity it went a long way," Zeller said.

Favorable action by the AFL-CIO on bringing the Teamsters back had been considered a foregone conclusion. Most of the presidents of the federation's 89 affiliated unions have reveled at the prospect of bolstering the AFL-CIO's membership by more than 12 percent after seeing its numbers erode a like amount since 1975.

"I'm glad to see that the AFL-CIO finally saw the light, particularly in the climate that we face," said Mo Biller, president of the 255,000-member American Postal Workers Union. "They're the largest, strongest union in the country and they belong here."

Kirkland acknowledged that some members of the AFL-CIO's hierarchy had voiced concerns about the Teamsters' image.

"I suppose we're in a Catch-22 situation," he said. But he added that under the government's proposed action, a trusteeship could be imposed on any number of institutions, "certainly the Chamber of Commerce or the New York Stock Exchange."

"The entire labor movement is under siege from all sides," said Wayne Glenn, president of the Paper Workers Union. "And frankly, we're tired of it. There's a growing mood to fight back."

The Teamsters were one of three unions expelled from the AFL-CIO in 1957 over allegations of corruption.

A White House Commission on Organized Crime in 1985 identified the Teamsters as one of four major US unions either controlled or heavily influenced by members of organized crime families.

The three other unions are AFL-CIO affiliates: the International Longshoremen's Association, the Hotel and Restaurant Employees Union and the Laborers Union.

Presser, meanwhile, was indicted by a federal grand jury last year on charges of participating in a payroll-padding scheme at a Cleveland Teamsters local that he also heads.

He has repeatedly proclaimed his innocence and accused the government of using "bully tactics" in an effort to destroy his union.